experimental assessment of fracture in rigid nanocomposite foams weakened by a pre-crack in mixed-mode i/ii

Rigid nanocomposite foams reinforced with nanoclay have low density and high mechanical strength. additionally, they offer improved thermal and fracture properties, making them attractive for advanced structural applications. this study, examines the effect of nanoclay content (0, 1, 2, and 3 wt%) on the mechanical and fracture behavior of rigid polyurethane (pur) foams under mixed-mode i/ii loading. the samples are produced using ultrasonic dispersion and subjected to uniaxial tensile and fracture experiments with asymmetric edge notch disc bend (aendb) specimens. fracture toughness and stress intensity factors are analyzed using finite element modeling (fem). the results show that adding up to 2 wt% of nanoclay enhances tensile and fracture resistance, while 3 wt% reduces strength due to nanoparticle agglomeration. significantly, the specimen with 2 wt% of nanoclay shows the best performance, with about 35% increase in tensile strength, 25% in fracture displacement, and up to 32% improvement in fracture load under mixed-mode i/ii conditions. in contrast, the 3 wt% sample exhibits reductions of about 18% in tensile properties and 16% in mixed-mode fracture load. these findings highlight the importance of optimizing nanoclay concentration to achieve superior fracture performance in rigid pur foams rigid nanocomposite foams reinforced with nanoclay have low density and high mechanical strength. additionally, they offer improved thermal and fracture properties, making them attractive for advanced structural applications. this study, examines the effect of nanoclay content (0, 1, 2, and 3 wt%) on the mechanical and fracture behavior of rigid polyurethane (pur) foams under mixed-mode i/ii loading. the samples are produced using ultrasonic dispersion and subjected to uniaxial tensile and fracture experiments with asymmetric edge notch disc bend (aendb) specimens. fracture toughness and stress intensity factors are analyzed using finite element modeling (fem). the results show that adding up to 2 wt% of nanoclay enhances tensile and fracture resistance, while 3 wt% reduces strength due to nanoparticle agglomeration. significantly, the specimen with 2 wt% of nanoclay shows the best performance, with about 35% increase in tensile strength, 25% in fracture displacement, and up to 32% improvement in fracture load under mixed-mode i/ii conditions. in contrast, the 3 wt% sample exhibits reductions of about 18% in tensile properties and 16% in mixed-mode fracture load. these findings highlight the importance of optimizing nanoclay concentration to achieve superior fracture performance in rigid pur foams